Foundation Industry Wastes for Cement Encapsulants

Radioactive waste from the nuclear industry is often encapsulated in concrete to protect people and the environment from contamination. However, traditional Portland cement-based concrete is not only energy intensive but also not always the most efficient material for encapsulating such waste. 

Materials technology company Lucideon is working with nuclear engineering and project management company NUVIA UK to develop an alternative cement technology that offers a lower carbon and more effective solution to storing hazardous waste. It also utilises waste from foundation industries in its formulation. 

With funding from the Transforming Foundation Industries Challenge, Lucideon and NUVIA UK have developed MALLET (MIDAR Augmented Lower-cost Lower-carbon Encapsulation Technique). MALLET builds on Lucideon’s geopolymer technology, MIDAR, which uses a low-temperature chemical reaction to produce a strong, stable cement.  

“Geopolymers are an attractive alternative to Portland cement due to their lower embodied energy and carbon footprints. They can also be made with foundation industry wastes, such as coal fly ash and ground granulated blast furnace slag,” explains project lead Stuart MacLachlan, Head of R&D at Lucideon. 

The project explored the ability of geopolymer cement to encapsulate a range of wastes – including solids, sludges, and oils – and experimented with formulations using foundation industry wastes as a key component.  

“Geopolymers are an attractive alternative to Portland cement due to their lower embodied energy and carbon footprints. They can also be made with foundation industry wastes, such as coal fly ash and ground granulated blast furnace slag.” 

“We developed waste acceptance criteria, such as does the concrete remain crack-free and does the waste remain within the concrete if submerged in liquid. We then assessed the formulations for the different types of waste according to those criteria,” says MacLachlan. 

Geopolymer cement can encapsulate hazardous waste both within the matrix and as a surrounding shell. Unlike Portland cement, which is activated by water, the chemical setting reaction of geopolymers means they offer the potential for greater encapsulation performance.  

MacLachlan explains: “Portland cement is typically limited to around 9 volume per cent oil within the formulation because the oil inhibits the setting action. MALLET is alkali-activated, so it allows you to incorporate much larger volumes. The properties can also be refined by adjusting the formulation.” 

For example, current methods for encapsulating sludge can accommodate approximately 30% by weight, whereas MALLET is reported to encapsulate 70%. “Better encapsulation means reduced volumes of cement,” adds MacLachlan. 

MALLET is generating considerable industry interest and Lucideon and NUVIA UK plan further testing, including radiation resistance, as well as scaling the technology.  

“NUVIA UK and Lucideon’s collaboration on MALLET has resulted in a potential game-changer for radioactive waste disposal,” says Adrian Davis-Johnston, Head of Research, Development and Innovation at NUVIA UK. “By maximising waste loading, MALLET will substantially reduce the disposal volume of several problematic wastes, resulting in cost savings to the UK taxpayer in the multiple hundreds of millions of pounds and significantly reduce the size of future disposal facilities.” 

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